# Relationship history for MSHA mine 0405656

Current hierarchy: **David B  Blomgren → B & B Materials Inc → Barstow Plant**

- Valid-time bounds: inclusive, date granularity
- Null end: open-ended in the upstream history row; not independent proof of present control
- Transaction-time observation: 2026-10-13T11:19:05.459773+00:00

## Valid-time edges

- **controller_controls_mine:** David B  Blomgren  et al → Barstow Plant; 1999-02-01 to current/open; source msha-controller-operator-history
- **operator_operates_mine:** B & B Materials Inc → Barstow Plant; 2005-09-12 to current/open; source msha-controller-operator-history
- **controller_controls_operator:** David B  Blomgren  et al → B & B Materials Inc; 2005-09-12 to current/open; source msha-controller-operator-history